A 3D lattice Boltzmann effective media study: Understanding the role of C-S-H and water saturation on the permeability of cement paste

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Authors

Colleges, School and Institutes

External organisations

  • Laboratory of Photonics and Interfaces, Department de Chimie, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland. ahmad@mpip-mainz.mpg.de
  • SURREY UNIVERSITY

Abstract

A 3D lattice Boltzmann model is developed and used to calculate the water and gas permeabilities of model cement pastes at different degrees of water saturation. In addition to permeable micron-sized capillary pores and impermeable solid inclusions, the lattice Boltzmann model comprises weakly-permeable nano-porous calcium silicate hydrate (C-S-H). The multi-scale problem is addressed by using an effective media approach based on the idea of partial bounce-back. The model cement paste microstructures are generated with the platform μic. The critical parameters, C-S-H density and capillary porosity, are taken from 1H nuclear magnetic resonance relaxation analysis. The distribution of water and air is defined according to the Kelvin-Laplace law. It is found that when the capillary porosity is completely saturated with a fluid (either water or gas), the calculated intrinsic permeability is in good agreement with measurements of gas permeability on dried samples (10-17-10-16 m2). However, as the water saturation is reduced, the calculated apparent water permeability decreases and spans the full range of experimentally measured values (10 -16-10-22 m2). It is concluded that the degree of capillary water saturation is the major cause for variation in experimental permeability measurements. It is further concluded that the role of the weakly-permeable C-S-H, omitted in earlier modelling studies, is critical for determining the permeability at low capillary saturation.

Details

Original languageEnglish
Article number085016
JournalModelling and Simulation in Materials Science and Engineering
Volume21
Issue number8
Publication statusPublished - 1 Dec 2013